Basics of purchase order  in oracle apps R12:

To create a PO we need below set-ups :

1)Create a User
2)define person
3)assign job
4)Assign manger if needed
5)assign above person in FND user
6)define buyer from purchasing responsibility
7)Check the approval assignment
8)check the approval group for above approval assignment
9)open purching periods
10)open GL and inventory periods
11)check Owner Can Approve  flag in setups -->document types and click on update symbol